Update dart (#19997)

Author: dart-github-bot

library/dart

@@ -1,9 +1,9 @@
 Maintainers: Alexander Thomas <[email protected]> (@athomas), Ivan Inozemtsev <[email protected]> (@iinozemtsev)
 GitRepo: https://github.com/dart-lang/dart-docker.git
 GitFetch: refs/heads/main
-GitCommit: 1dfd9d9d5edd76682443355ca989acb8f9508e69
+GitCommit: b2bc5989a535e4c1fc8205ee102e2f32ca79e5e6
 
-Tags: 3.9.3-sdk, 3.9-sdk, 3-sdk, stable-sdk, sdk, 3.9.3, 3.9, 3, stable, latest
+Tags: 3.9.4-sdk, 3.9-sdk, 3-sdk, stable-sdk, sdk, 3.9.4, 3.9, 3, stable, latest
 Architectures: amd64, arm32v7, arm64v8, riscv64
 Directory: stable/trixie